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CATERPILLAR MONITORING SYSTEM

This illustration shows the the relationship of the Caterpillar Monitoring System to the other
ECMs on the "H" Series Wheel Loaders. Information displayed on the Caterpillar Monitoring
System is sent to the main display module from input components in the monitoring system.
Information is also received by the monitoring system from the Transmission ECM, the Engine
ECM, and the Implement ECM over the CAT Data Link.

The "H" Series Wheel Loaders use a programmable Caterpillar Monitoring System main
display module, which enables installation of updated software that may include future control
system features.
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3

186

6
5

187

Fuel Level Sender

The fuel level sender (1) is located on the top of the fuel tank (4) on the right side of the
machine. The sender can be accessed by raising the engine hood.
The sender measures the depth of fuel in the tank. The fuel level sender has an internal
resistance between 28 and 250 Ohms and is connected to pin 9 and the Cat Monitoring System
ECM. The quad gauge displays the fuel level on the fuel level gauge.
The upper illustration shows the location of the sender in comparison to the rear frame (2) and
the fuel tank (4). The lower illustration also shows the float (5) and the variable resistor (6).
Also shown is the fuel fill cap (3).
NOTE: The fuel level sender can be serviced separately from the float assembly.
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Hydraulic Oil Temperature Sensor

The hydraulic oil temperature sensor (1) is located in the lower end of the hydraulic tank (2).
The sensor is a passive temperature sensor with a thermistor at the tip. The voltage output will
decrease as the temperature increases in the tank. The signal from the sensor is connected to
pin 10 on the Cat Monitoring System ECM (not shown).
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191

1
2

Service Brake Pressure Switch

The upper illustration shows the location of the accumulator charging valve (1).

The service brake pressure switch (2) is located on the right side of the machine below the
Engine ECM (4) on the accumulator charging valve. The pressure type switch contacts are
normally open. When the engine is running, the switch contacts are made when the brake
accumulator oil pressure increases to approximately 8270 kpa (1200 psi). If the brake pressure
decreases to approximately 6890 kPa (1000 psi), the switch contacts will open. The brake oil
pressure alert will begin flashing on the main display module.
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192

2
193

Axle Oil Temperature Sensors

The above illustrations show the location of the axle oil temperature sensors in each axle. The
upper illustration shows the temperature sensor (1) located in the front differential. The lower
illustration shows the temperature sensor (2) located in the rear differential. The sensors are
passive temperature sensor with a thermistor at the tip. The sensors produce a voltage output
which decreases as the oil temperature in the respective differential increases.

The front and rear axle temperature sensors relay the temperature data to the Cat Monitoring
System.
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4

9
8
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10

Differential Pressure Switches In The Right Side Service Bay

The top illustration shows the hydraulic system return filter with the hydraulic oil fluid
sampling port (3) (blue color) located on the filter base (1). Also, located on the filter base is
the pressure differential switch (2) which signals the Cat Monitoring System when the filter is
bypassing. The bypass switch actuates at 138 kPa (20 psi).

Also, shown is the manual lowering valve (4) and the brake accumulators (5).
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The lower illustrations shows the location of the fluid sampling port (8) (purple color) and the
pressure tap (9) (black color) for the power train system. The sampling port is located on the
filter base (7) along with the power train pressure differential switch (6). The filter base is the
pressure differential switch (6) signals the Cat Monitoring System when the filter is bypassing.
The bypass switch actuates at 276 kPa (40 psi).

Also shown is the ecology drain (10) for the hydraulic tank.
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196

Action Alarm

The action alarm (1) is an output of the Cat Monitoring System (pin 4). When the action alarm
is audible, the machine needs immediate attention. A safe machine shutdown is required. The
main display module will sound the action alarm whenever a warning category 3 problem
exists. An alarm for a warning category 3 is a pulsating sound. The alarm for a warning
category 2S is a continuous tone.

The action alarm does not operate when the engine is stopped. The main display module uses
functions in order to determine when the engine is running. The following functions are
examples: engine oil pressure, alternator speed and engine speed. If necessary, the action
alarm SOUNDS when the main display module decides that the engine is running.

The action alarm is located behind the operator’s seat next to the implement ECM (2).
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Fuel Level Indicator

The fuel pressure indicator (arrow) is located on the left side of the dash panel. This indicator
illuminates if the fuel level is low.
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2

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Torque Converter Outlet Temperature Sensor

The torque converter outlet temperature sensor (1) is a passive sensor that sends an input
temperature signal to Cat Monitoring System. The monitoring system interprets the
temperature signal and moves the needle for the transmission oil temperature indicator (4) to
reflect the oil temperature.

Also shown in the top illustration is the implement pump (2) and the transmission oil
temperature sensor (3).
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Electrical System

The indicator (1) for the electrical system will illuminate when there is a malfunction in the
electrical system. The system voltage is too high for normal machine operation or the system
voltage is too low for normal machine operation.

If the electrical loads are high with low engine speed, then increase output from the
alternator (2). If the alert indicator for the electrical system turns off within one minute, the
electrical system is operating normally.

Overloading may occur during periods of low engine speeds. Revise the operating cycle in
order to avoid overloading the electrical system. Overloading the electrical system could result
in discharging the batteries.
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If this procedure does not cause the alert indicator to turn off, stop the machine and investigate
the cause of the fault. The fault may be caused by an alternator belt that is loose or broken.
Also, the batteries may be faulty.

If the indicator remains on or near normal operating speeds and with light electrical loads, stop
the machine and investigate the cause of the fault. The fault may be caused by an alternator belt
that is loose or broken. Also, the batteries or the alternator may be faulty.

The electrical indicator is connected to the "R" (3) contact on the alternator.
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Engine Tachometer

The tachometer (arrow), located on the front dash panel, shows an analog display of the engine
speed in both rpm and km/h. The engine speed is determined by the information sent to the Cat
Monitoring System module over the Cat Data Link from the Engine ECM.

The crankshaft speed timing sensor and the camshaft speed timing sensor initiate the input
signals to the Engine ECM.

The Cat Monitoring System also sends the module clock signal and the data signal to the
tachometer module.